Robert Kubica has revealed his rivals accused him of doping when he won karting championships in Italy early in his career.

The Pole has always been considered one of the top talents of his generation along with the likes of Lewis Hamilton and Sebastian Vettel, who have 10 Formula 1 titles between them.

Unfortunately, his rally crash in 2011 meant Kubica never reached the heights most expected him to, but when he was starting to show his potential as a teenager, others were sceptical.

"In Italy, all the major championships were held and then suddenly I won the Italian Championship in 1998 and 1999. I was the first foreigner to do so," he recalled speaking to Pirelli's Mario Isola on Instagram.

"My rivals didn't believe it and thought I was doping, but I think I was just very smart for my age, which helped me a lot while racing."

Indeed, coming from Poland, Kubica admitted he didn't have the backing or the equipment of some of those he was competing against and even surprised himself with his ability.

"Everyone had great karts and outfits and then I arrived with my white helmet and old kart that only had my name on it. I only had my father and one engineer to help me, where others were present with whole teams," he said.

"I would just follow the fastest driver and see how he drove his lap, that was easy. I told my dad it was not so bad, but he said 'he held back'.

"Not much later I was on pole, so I was much faster anyway.

''It was only then that I realized I was much better than everyone told me. I just wanted to make it to the finals, but finished second.

"In my whole career, I haven't been as good as in karting," Kubica concluded.